Printing error when using PARAMS in Rails - ruby-on-rails

Question

For my API in RAILS I have programmed a code that basically does the following.
class Api::V1::NameController < ApplicationController
skip_before_filter :verify_authenticity_token
def index
end
def create
# Loading data
data_1_W = params[:data1]
data_2_W = params[:data2]
while len > i
# -Here I do some calculations with data_1_W and data_2_W.
# Its not important to show the code here
end
# -Organizing outputs to obtain only one JSON-
# Its not important to show the code here
# Finally HTTP responses
if check_error == 1
render status: 200, json: {
message: "Succesful data calculation",
data_output: response_hash
}.to_json
end
end
end
To test that everything is working I use the cURL command. I notice that loading the data could be a problem and therefore the code would break.
I want to tell the user that it was an error loading the data for some reason (HTTP response), but I don't know where to put it. If I put and else under my success status it would not print it because the code breaks just starting (instead of sending the correct name - d '#data.json' of the data in cURL I send -d '#dat.json').
The data I am loading is a JSON data {"data1":[{"name1":"value1"},{"name2":number2}...],"data2":[{"name1":"value1"},{"name2":number2...}]}. (This data has 70080 rows with 2 columns if we see it as a table, which I divided into two in my CODE for calculations purposes data_1_W and data_2_W)
Could anyone help me where to put it? more or less like this:
render status: 500, json: {
message: "Error loading the data",
}.to_json

Answer 1

Put it in a rescue block around the code that throws the error.
E.g.
def func
# code that raises exception
rescue SomeException => e
# render 422
end

Answer 2

Since you are working in Rails I'd recommend going the rails way. This means that I would create some kind of service and initialize it in the create action.
Now, within the service you do all you funky stuff (which also allows you to clean this controller and make i look prettier) and the moment a condition is not fulfilled in that service return false. So...
# controllers/api/v1/name_controller.rb
...
def create
meaningful_variable_name = YourFunkyService.new(args)
if meaningful_variable_name.perform # since you are in create then I assume you're creating some kind of resource
#do something
else
render json: {
error: "Your error",
status: error_code, # I don't think you want to return 500. Since you're the one handling it
}
end
end
# services/api/v1/your_funky_service.rb
class Api::V1::YourFunkyService
def initiliaze(params)
#params = params
end
def perfom #call it save if you wish
....
return false if check_error == 1
end
end